LibraryThing

I enjoyed the LibraryThing site. It is good to be able to change some things about how the book is catalogued. I particuarly enjoyed that I was able to find the book my grandfather wrote (with more than one listing) as it is not a well known book.

Del.icio.us

I found the Del.icio.us site rather confusing. There was too much going on. I personally wouldn't use it. The site would an absolute last resort for me within the library.